A photovoltaic device is one which converts sunlight directly into electricity. Although photovoltaic devices are not yet in widespread use in applications which require the generation of large amounts of electricity, such as electrical power plants, they have come into daily usage in applications where only small amounts of current are required. For example, photovoltaic devices are common in such consumer items as calculators, watches, outdoor lighting, etc. Typically, these products have the photovoltaic devices built in so that a continuous supply of electricity is available to power the various items as long as the solar cells are exposed to light. Storage devices, such as solar batteries, may be provided to store the generated electricity during periods of darkness.
Obviously, it is the convenience of such consumer items that has made them popular. By incorporating the power source directly into the product, the ultimate in convenience is achieved.
There are other applications wherein a built-in source of continuous electrical power would be extremely useful. For example, cars which are left outside for long periods of time (such as in airport parking lots) often experience starting problems due to low battery levels. Hence, a variety of photovoltaic devices which may be connected to the electrical system of the car (such as via the cigarette lighter) may be used to trickle charge the battery. See, for example, U.S. Pat. No. 4,327,396. Similarly, automobiles which are parked out in the hot sun for even short periods of time absorb sufficient solar energy to raise the interior temperature to uncomfortable levels. Small fans which draw low levels of power are available on the market to exhaust the solar heated air from the car's interior and circulate cooler, outside air. Such fans can be powered the car's electrical system, or can be solar powered.
Houses and other buildings could also benefit from a source of electricity provided by photovoltaic devices which is independent of the building's central power supply. For example, in cases of power outage, it would be extremely useful to have an auxiliary source of electrical power.
Of course, there are various photovoltaic modules available on the market which can be used in both building and vehicular applications to generate auxiliary power. However, these modules have not come into widespread use for a variety of reasons. See, for example, U.S. Pat. Nos.: 4,724,010; 4,475,031; and 4,773,944. Important disadvantages are that they tend to be unsightly, or are add-ons, which are inconvenient and space-consuming.
It would desirable to provide an auxiliary source of power which may easily be incorporated into buildings, vehicles, and the like, either when they are manufactured or as a retrofit. However, in order to be commercially successful, such a product should ideally integrate both aesthetically and structurally with the building or vehicle and should not be obtrusive, unsightly, or inconvenient to use.